I think they made a simple mistake. I usually start them under lights for anywhere from 12-16 hours on, the rest off. I think I set my timer for 12 or 14.
Plants need an off period, this is when they grow. There was a study done about 50 years ago about which on/off length is best, I will try to find the pic if I didn't post it yet.
Here it is:(http://mysite.verizon.net/~korney19/301.jpg)